Pokemon Platinum Cheats :

This cheat for Pokemon Platinum [Nintendo DS] has been posted at 31 Aug 2009 by insane321 and is called "Easy lvl up in day care". The Cheat have a rating 2 by 4 our users and has been commented 6 times. If cheat is usable don't forgot thumbs up insane321 and share this with your freinds. And most important we have 179 other cheats for Pokemon Platinum, look them as soon as possible!

Secret - Easy lvl up in day care

Ok so put some pkmn u want to lvl up in the daycare, next tape down the up button when facing a slope u'd need a bike for(also tape down b button), now put ur ds on the charger, over night ur pkmn will grow, (only if u keep the game on), u should do this for pkmn lvl 1- 35 cause after that they wont grow very fast at all.

It works if all you're going for is levels. The only thing wrong is that if you want to maximize stats, you don't want to do this. The exp.share method is what you want if you're going for EVs.
I'm not trying to debunk your method, I'm just saying it's not worth it in the long run.
Take this for instance: I put a Chansey in the daycare. For one, you cannot evolve your Chansey into the more sought after Blissey if you don't train it yourself. It may be gaining levels, but if it doesn't gain levels while in your party, it's happiness is not raised. Reason two, the reason people use Chansey is because of it's huge amount of HP. By keeping it in the daycare, you're lowering it's max HP capabilities. By way of exp.share, the EVs your pokemon need to max out their stats will be earned without having to fight, which comes in handy when training the Happiny/Chansey/Blissey trio due to their horrible attack power and inability to naturally learn specialty attacks, in which they're better at using.
This is just one example that I've experienced first hand.